This proposal is part of a continuing effort to understand how the Drosophila embryo regulates the usage of its maternal-message. We have prepared a small library of clones containing Drosphila genomic DNA inserts. This library will be screened three times to detect inserts complementary to cytoplasmic poly A plus RNA prepared from oocytes, gastrula and prehatching embryos. Eighteen such clones have already been identified. These clones are complementary to abundant and midabundant poly A plus RNA present at all three stages of development. A number of these clones will be selected for biochemical characterization, including such things as the size of insert DNA, size of the coding region and size of nuclear RNA products. The clones will be mapped by in situ hybridization to salivary gland chromosomes. In addition, I will use these as probes of biological function including the determination of the poly A plus/poly A minus ratio, changes in abundance of cytoplasmic and nuclear RNA and the polysomal/nonpolysomal ratio of each clones probe. A clone containing the putative amy gene has been identified and will be characterized.